Chart assignment

Charts to read and discuss

Read each chart, then answer its questions. Every chart shows its source and date; open it for a table of the numbers and the data to download.

  1. What causes most flight delays?
  2. Are U.S. roads getting safer per mile driven?

Chart 1 of 2 · Air travel

What causes most flight delays?

The interactive chart needs JavaScript. The numbers are on the chart's page.

In the 12 months through August 2026, 39.8% of all minutes of delay came from a late-arriving aircraft: a plane that left its last airport late. The airline itself (crew, maintenance, cleaning, fueling) caused 32.9%, the air traffic system 21.1% and severe weather 6%. Weather also hides in the other causes: BTS counts ordinary weather that slows traffic under the air traffic system.

Questions to discuss

  1. In one sentence of your own, what does this chart show?
  2. Find the biggest change or difference in the chart. What might explain it?
  3. Who collected these numbers, and how recent are they? What else would you want to know before drawing a conclusion?

Source: U.S. Bureau of Transportation Statistics, Airline On-Time Performance (Reporting Carrier On-Time Performance, 1987–present) (Public domain (U.S. government work)) · Data as of Aug 31, 2026

Open the chart and its numbers

Chart 2 of 2 · Road safety

Are U.S. roads getting safer per mile driven?

The interactive chart needs JavaScript. The numbers are on the chart's page.

In 2024 there were 1.19 deaths for every 100 million miles driven, down from 3.35 in 1980. The lowest rate was 1.08 in 2014; it jumped to 1.34 in 2020, when people drove less but deaths rose. Miles driven are the Federal Highway Administration's estimates.

How to read this chart

Each point is the number of people killed in traffic crashes for every 100 million miles Americans drove that year. Dividing by miles driven turns a count into a rate, so years when people drove more or less can be compared fairly.

Questions to discuss

  1. About what fraction of the 1980 rate is the rate in the latest year?
  2. In 2020 people drove less, but the rate went up. What could explain that?
  3. Why is deaths per mile a fairer way to compare years than the total number of deaths?

Source: NHTSA Fatality Analysis Reporting System (FARS) and FHWA Highway Statistics (table VM-2) (Public domain (U.S. government work)) · Data as of Dec 31, 2024

Open the chart and its numbers

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